The Deep Space Network
1958-present
Who
NASA/JPL's worldwide network of giant radio antennas - the only phone line to the outer Solar System.
Why it matters
Three complexes sit about 120 degrees apart - Goldstone (California), Madrid (Spain) and Canberra (Australia) - so that a distant spacecraft is always in view of at least one, no matter where the Earth has rotated. Their 70-metre, 34-metre and 26-metre antennas have talked to every deep-space mission since the 1960s: the Mariners, the Viking landers, Voyager, Cassini, and the probes still calling home today. It is also an observatory: by tracking a spacecraft's signal with atomic-clock precision, the same antennas measure planets' gravity fields and atmospheres - radio science.
Lineage
Built on radar and radio astronomy, and on the rocketry heritage of JPL. Enabled radio science as a discipline (see the Viking card), the navigation of every deep-space probe, and the live link behind broadcasts like Apollo 12's TV.